This application relates to and claims a priority from corresponding Japanese Patent Application No. 2000-236688 filed on Aug. 4, 2000.
1. Field of the Invention
The present invention relates to an indication and an input of coordinate positions of a position pointing device which is used in, for example, an optical digitizer. More particularly, it relates to a position detection device in which the indication and input of the coordinate positions are controlled in accordance with the changes in the pressing or contact pressure of the pen tip of a position pointing device with respect to the position detection surface.
2. Description of the Related Art
Conventionally, there has been proposed a coordinate input device wherein incident angles of light coming from the position pointing device are detected at different two positions and then the coordinate of the pointed position is obtained based on the triangular principle. Such coordinate input device using the light is generally called an optical type digitizer.
As a typical optical digitizer, Japanese Patent Application Kokai Publication No. Hei 3-5805 discloses an optical system wherein such light beam as a laser beam is rotated by a rotation mirror and a retroreflected light coming back in the reverse passage from the position pointing device is detected. This type of system has been put to practical use in, for example, black boards.
For example, Japanese Patent Application Kokai Publication No. Hei 9-319501 discloses a system wherein a light emitting diode (LED) is used as a light emitting means and a retroreflective member is provided to a position pointing device, and wherein the receiving light angle of the reflected light coming back after being retroreflected by the retroreflective member onto which the light from the LED incidents is detected by a position sensing device (PSD). The PSD is a non-divided element and is capable of directly obtaining a coordinate value in the form of ratio of voltage values or current values.
As a further example, Japanese Patent Application Kokai Publication No. Hei 11-85378 discloses a system in which the position pointing device itself is provided with such a point light source as an LED and a detection means for detecting writing pressure, and in which a two-part divided light receiving element is used for the light receiving section. In this example, the device is so arranged that the necessary light detection angle is obtained by causing the position of the two-part divided light receiving element to move by a driver means and necessary writing pressure is obtained by the writing pressure detection means. The position pointing device in this example requires an electronic circuit device and a battery, for example, for supplying power to the LED and for detecting the wiring pressure.
As a still further example, Japanese Patent Application Kokai Publication No. Hei 11-3170 discloses a system wherein the position pointing device itself is provided with three color light emitting means such as three color LEDs and a writing pressure detection means, or a reflection type method wherein the position pointing device itself is provided with a colored retroreflective member and the reflected light therefrom is used and one-dimensional light receiving element is arranged as a light receiving section. In this example, any of the three color LEDs is turned on to emit light in accordance with the magnitude of the writing pressure whereby the position coordinate is obtained based on the emitted light itself and the writing pressure information is obtained based on the color tone or hue of the light. In the case where the colored retroreflective member is arranged step by step in color tone at the tip portion of the position pointing device, the position coordinate and the writing pressure are obtained based on the changes in light and color in accordance with the up and down movements by the writing pressure.
In the example disclosed in the above Japanese Patent Application Kokai Publication No. Hei 11-3170, there is a problem in that the information concerning the position coordinate and the writing pressure becomes unstable in accordance with the changes in height or inclination of the position pointing device with respect to the contact plain.
Generally, in the optical digitizer, the height of light emitting point of the light discharging means is not at the same level as the surface of the coordinate detection region. Since the light emitting point is required to be at a certain height, it follows that the position pointing device is detected before such device reaches the surface of the coordinate detection region. This undesirable detection causes the occurrence of an erroneous input or erroneous operation, or in the case of an input operation of letters, causes the occurrence of phenomena in which lines or dots become blurred because of no breaks of lines or dots. In order to cope with this problem, there are some examples in which a pen-down of the pointing device is detected through such methods as writing pressure detection means.
However, to use methods by which the pen-down is detected by a sensor, or a switch is caused to be ON, it is necessary for a position pointing device to have a built-in detection sensor or switch means, and to have electronic circuits and batteries for transmitting the pen-down detection signals (with such as infrared rays and weak electric waves). Also, on the side at which the signals are received and processed, it is necessary to arrange electronic circuits for the reception of the signals. A position pointing device requires complicated construction and an increased number of component parts, thus resulting in a costly pointing device.
Also, it is necessary to change sometimes the battery because of the life thereof. Further, there is a problem that, depending on the changes in the height and inclination of the position pointing device, the position of coordinate and the writing pressure information become unstable.
The present invention came about in order to overcome the above described problems in the prior art, and provides a position detection device in which the detection of the pen-down and pen-up of the position pointing device with respect to the surface of the position detection region can be performed stably, and provides a durable position detection device at a low cost. Throughout the specification, the word xe2x80x9cpen-upxe2x80x9d is used to mean a state wherein the tip of the position pointing device is not in contact with the surface of the coordinate position detection area, whereas the word xe2x80x9cpen-downxe2x80x9d is used to mean a state wherein the tip is in contact with the surface.
In order to attain the above purposes, the present invention provides a position detection device which is configured by: a position pointing means having a light reflecting means; a light emitting means for emitting light to the light reflecting means of the position pointing means; a light receiving means for receiving light from the light reflecting means of the position pointing means; and a coordinate calculation means for calculating the position coordinate of the position pointing means based on information from the light receiving means, the position detection device being characterized in that:
the position pointing means has a pen-like shape, and has a movable pen-core portion changeable in its position according to the pressing pressure against the surface of a board, and a light modulation means for changing the characteristics of the reflection light, and a transmission means for transmitting to the light modulation means the displacement of the movable pen-core portion; and
the light receiving means has an up/down state detection means for obtaining up- and down-state information of the position pointing means by detecting-the characteristics of light which have been changed by the light modulation means.
The necessary modulation of light mentioned above can be effected by shielding or blocking a part of the light, and it can also be achieved by the adjustment of the effective reflection area, or of the reflection intensity.
Further, the light modulation may be continuously performed in accordance with the magnitude of the pressing pressure against the board surface.
According to another aspect of the invention, there is provided a position pointing means used in an optical position detection device, the position pointing means having a pen-like shape, and comprising:
a movable pen-core portion subject to displacement by pressure on a board;
a light modulation means for changing characteristics of reflection light; and
a transmission means for transmitting the displacement of the movable pen-core portion to the light modulation means.
According to a further aspect of the invention, there is provided a position detection method using a position detection device which comprises: a position pointing means having a movable pen-core portion and a light reflection means having a retroreflective member; a light emitting means for emitting the light to the light reflection means; a light receiving means for receiving the light from the light reflection means of the position pointing means; and a coordinate calculation means for calculating a position coordinate of the position pointing means based on information from the light receiving means, the method comprising the steps of:
emitting light from the light emitting means to the light reflection means of the position pointing means;
modulating light for changing characteristics of reflection light of the light reflection means based on displacement of the movable pen-core portion produced from the pressure of the position pointing means by an operator onto a coordinate detection surface of the position detection device; and
detecting a pen-down state for obtaining the pen-up and pen-down information of the position pointing means by detecting with the light receiving means characteristics of the light changed by the light modulation means.